SEISMIC ISOLATION BY MECHANICAL FILTERS AT VERY-LOW FREQUENCIES

The VIRGO SuperAttenuator is a complex six-degrees of freedom remote-c ontrolled mechanism that isolates a 80 kg payload from environmental p erturbations, such as the seismic noise. It consists of a Pre-Isolator stage, a chain of mechanical filters and a last stage, holding the pa yload. The Pre-Isolator and the fiiters are essentially harmonic oscil lators with a low resonant frequency. The filters are designed to work below 500 mHz in all degrees of freedom. During the last year, a Pre- Isolator with resonant frequencies of 30 mHz in three degrees of freed om has been engineered and built. Intensive studies on the long-term s pring behaviour have been performed to find a metal suitable to be str essed up to 1 kN/mm(2) with no evidence of creep. (C) 1998 Elsevier Sc ience B.V. All rights reserved.